Multimetallic and mixed environment iridium(III) complexes : a modular approach to luminescence tuning using a host platform

Abstract

Mononuclear and trinuclear bis-cyclometalled Ir(III)complexes of the host ligands tris(4-[4’-methyl-2,2’-bipyridyl]methyl)cyclotriguaiacylene (L1) and tris(4-(4’-methyl-2,2’-bipyridyl)carboxy)cyclotriguaiacylene (L2) have been prepared. Complexes [{Ir(ppy)2}3(L1)](PF6)3 1.1, [{Ir(ppy)2}(L1)](PF6)31.2,[{Ir(ppy)2}3(L2)](PF6)3 2.1 and [{Ir(ppy)2}(L2)](PF6)3 2.2 (where ppy =phenylpyridinato) showed distinct photophysical properties according to L-ligand with L1 complexes comparatively blue-shifted in solution, with longer lifetimes and higher quantum yields. The mixed bis-cyclometallated Ir(III) complexes [{Ir(ppy)2}{Ir(dFppy)2}2(L1)](PF6)3 1.3,, [{Ir(ppy)2}{Ir(dFppy)2}2(L2)](PF6)3 2.3,[{Ir(ppy)2}2{Ir(dFppy)2}(L1)](PF6)3 1.4 and[{Ir(ppy)2}2{Ir(dFppy)2}(L2)](PF6)3 2.4 (where dFppy = 2,4-difluorophenylpyrinato) were also synthesised. Steady-state and time-resolved spectroscopy along with electrochemical investigation show that Ir(C^N)2 chromophores within these mixed Ir-environment species behave as isolated centres with no energy transfer or electronic communication between them.